Advanced receiver autonomous integrity monitoring (ARAIM) is developed on the basis of receiver autonomous integrity monitoring (RAIM). The availability of a satellite navigation system used by an aerial craft in a flight phase can be evaluated by ARAIM according to satellite measurement data received by a receiver and ground integrity support information (ISM). When an evaluation result shows that ARAIM fails to meet the integrity requirement for navigation performance needed in a flight phase of an aerial craft, the aerial craft has to use a roadbed navigation apparatus in the flight phase, rather than the satellite navigation system.
An existing method based on ARAIM for evaluating the availability of a satellite navigation system comprises the following steps: calculating a horizontal protection level (HPL), a vertical protection level (VPL), and an effective monitor threshold (EMT) espectivley according to satellite measurement data received by a receiver and preset ISM, comparing the obtained HPL, VPL, and EMT respectively with a preset HPL threshold, a preset VPL threshold, and a preset EMT threshold, and determining an evaluation result according to a comparison result.
However, by means of the existing ARAIM, only the availability of a satellite navigation system at a current time point can be evaluated according to satellite measurement data received at the current time point, and the availability of the satellite navigation system at a time point next to the current time point cannot be evaluated, which is not conducive to the availability evaluation of the satellite navigation system at the time when an aerial craft is on a long-distance flight.